Writer core incorporating thermal sensor having a temperature coefficient of resistance

ABSTRACT

A writer core of a transducer is configured to interact with a magnetic recording medium and comprises an upper core and a lower core. At least one of the upper and lower cores comprises a return pole having a return shield. The apparatus also comprises a writer pole between the upper and lower cores, and a writer gap defined between the writer pole and the return shield. The apparatus further comprises a sensor element within one of the upper and lower cores that includes the writer gap. The sensor element has a temperature coefficient of resistance and is configured to sense for a change in temperature indicative of one or both of a change in spacing and contact between the transducer and the magnetic recording medium.

SUMMARY

Embodiments of the disclosure are directed to an apparatus comprising awriter core of a transducer configured to interact with a magneticrecording medium and comprising an upper core and a lower core. At leastone of the upper and lower cores comprises a return pole having a returnshield. The apparatus also comprises a writer pole between the upper andlower cores, and a writer gap defined between the writer pole and thereturn shield. The apparatus further comprises a sensor element withinone of the upper and lower cores that includes the writer gap. Thesensor element has a temperature coefficient of resistance and isconfigured to sense for a change in temperature indicative of one orboth of a change in spacing and contact between the transducer and themagnetic recording medium.

Other embodiments are directed to an apparatus comprising a writer coreof a transducer configured to interact with a magnetic recording mediumand comprising an upper core and a lower core. At least one of the upperand lower cores comprises a return pole having a return shield. Theapparatus also comprise a writer pole between the upper and lower cores,and a writer gap defined between the writer pole and the return shield.The apparatus further comprises a sensor element within one of the upperand lower cores that includes the writer gap. The sensor element has atemperature coefficient of resistance and is configured to sense for achange in temperature indicative of one or both of a change in spacingand contact between the transducer and the magnetic recording medium,and to enhance a gradient of a magnetic field generated by the writecore.

Further embodiments are directed to a method involving sensing atemperature at or near a return shield of a writer core of a transducer,measuring a change in the sensed temperature indicative of a change inspacing or contact between the transducer and an magnetic recordingmedium, and performing a predetermined action in response to themeasured temperature change. In some embodiments, the predeterminedaction comprises declaring a contact event between the transducer andthe medium. Other embodiments involve sensing the temperature at or nearthe return shield using a thermal sensor and enhancing a gradient of amagnetic field produced by the writer core using a magnetic fieldproduced by the thermal sensor.

These and other features and aspects of various embodiments may beunderstood in view of the following detailed discussion and accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified illustration of a recording transducer shown inclose proximity to a rotating magnetic storage medium in accordance withvarious embodiments;

FIGS. 2 and 3 are flow diagrams illustrating methods of detectinghead-medium contact in accordance with various embodiments;

FIG. 4 is a flow diagram illustrating a method of using a thermal sensorfor both detecting head-medium contact and synchronizing the magneticresponse of a writer pole and shield(s) when writing data to a magneticrecording medium in accordance with various embodiments;

FIG. 5A is a sectional view of a writer core of a transducer thatincorporates a thermal sensor in accordance with various embodiments;

FIG. 5B is an exploded sectional view of an upper writer core portion ofa transducer that incorporates a thermal sensor in accordance withvarious embodiments;

FIG. 6 shows a portion of a thermal sensor which can be incorporatedwithin a writer core of a transducer in accordance with variousembodiments;

FIG. 7 is a sectional view of a writer core of a transducer thatincorporates a thermal sensor and circuitry that controllably powers thewriter core and thermal sensor in accordance with various embodiments;and

FIG. 8 illustrates a recording transducer which includes a multiplicityof thermal sensors in accordance with various embodiments.

DETAILED DESCRIPTION

In the following description, reference is made to the accompanying setof drawings that form a part of the description hereof and in which areshown by way of illustration several specific embodiments. It is to beunderstood that other embodiments are contemplated and may be madewithout departing from the scope of the present disclosure. Thefollowing detailed description, therefore, is not to be taken in alimiting sense.

Unless otherwise indicated, all numbers expressing feature sizes,amounts, and physical properties used in the specification and claimsare to be understood as being modified in all instances by the term“about.” Accordingly, unless indicated to the contrary, the numericalparameters set forth in the foregoing specification and attached claimsare approximations that can vary depending upon the desired propertiessought to be obtained by those skilled in the art utilizing theteachings disclosed herein. The use of numerical ranges by endpointsincludes all numbers within that range (e.g. 1 to 5 includes 1, 1.5, 2,2.75, 3, 3.80, 4, and 5) and any range within that range.

Data storage systems commonly include one or more recording heads thatwrite and read information to and from a recording medium. A relativelysmall distance or spacing is maintained between a recording head and itsassociated media. This distance or spacing is known as “fly height” or“head-media spacing.” By reducing the head-media spacing, a recordinghead is typically better able to both write and read data to and from amedium. Reducing the head-media spacing also allows for surveying ofrecording medium topography, such as for detecting asperities, voids,and other features of the recording medium surface. Head-media contactdetection and/or head-media spacing sensing technologies are importantfor the performance and reliability of magnetic storage systems. Highercontact detection repeatability enables lower active clearance, and thushigher recording density. Higher contact detection sensitivity reduceswear and improves reliability.

In accordance with various embodiments, and with reference to FIG. 1, arecording transducer 100 is shown in close proximity to a rotatingmagnetic storage medium 101. The recording transducer 100 includes anumber of components, including a writer 110, a writer heater 112thermally coupled to the writer 110, a reader 140, and a reader heater142 thermally coupled to the reader 140. The writer 110 and reader 140are positioned at or near an air bearing surface (ABS) 105 of thetransducer 100. The heaters 112 and 142 may be resistive heaters thatgenerate heat in response to passage of electrical current. The thermalenergy generated by the heaters 112 and 142 causes thermal expansion ofthe transducer 100, largely expressed at the ABS 105. In particular,actuation of the writer heater 112 causes thermal expansion of thewriter region of the transducer 100, resulting in reduced spacingbetween the writer 110 and the magnetic recording medium 101. Similarly,actuation of the reader heater 142 causes thermal expansion of thereader region of the transducer 100, resulting in reduced spacingbetween the reader 140 and the magnetic recording medium 101.Selectively actuating the writer and reader heaters 112 and 142 allowsfor control of the head-media spacing in a data storage system.

Providing robust contact detection at the writer region of thetransducer 100 can be challenging, particularly in conventionaltransducer designs that employ thermal actuation of the writer and acontact sensor located remotely from the writer pole. In general, it isdifficult or impossible to place a contact sensor next to the writerpole in a conventional design due to the complicated writer structure.Touchdown signals from a conventional contact sensor become even weakerfor non-modulating or low-clearance air bearing designs.

Embodiments of the disclosure are directed to a magnetic writer thatincorporates a thermal sensor within the writer core in close proximityto the writer pole of the magnetic writer. Some embodiments are directedto a magnetic writer that incorporates a thermal sensor near a shield ofthe magnetic writer proximate the writer pole. Other embodiments aredirected to a magnetic writer that incorporates a thermal sensorintegral to (within, inside of, embedded in or otherwise physicallyconnected to) a shield of the magnetic writer proximate the writer pole.By utilizing the AC or DC component of the resistive change of thethermal sensor, writer spacing changes and touchdowns, particularly fora thermally actuated writer, can be declared with an improved contactsignal-to-noise ratio and accuracy.

Further embodiments are directed to a magnetic writer that incorporatesa multifunctional thermal sensor at or within a writer core of themagnetic writer. In one mode of operation, for example, themultifunctional thermal sensor serves to sense changes in head-mediaspacing and contact events. In a second mode of operation, themultifunctional thermal sensor serves to enhance or optimize themagnetic field gradient during a writing event. For example, themultifunctional thermal sensor serves to synchronize the magneticresponse of the writer pole and return shield when writing data to amagnetic recording medium. Various embodiments are directed tohead-media spacing and contact detection apparatuses and methods for usewith modulating air bearings. Other embodiments are directed tohead-media spacing and contact detection apparatuses and methods for usewith air bearings with low head-media spacing modulation or head-diskinterfaces with stiff air bearings.

According to various embodiments, the writer 110 incorporates a thermalsensor 116 positioned in close proximity to a writer pole 120. In someembodiments, the thermal sensor 116 is incorporated within the writercore of the writer 110, such as near or within a shield of the writer110. In other embodiments, the thermal sensor 116 is incorporated withinthe portion of the writer core that includes a write gap defined betweenthe writer pole 120 and a return shield of the writer 110. Placement ofthe thermal sensor 116 within the writer core and in close proximity tothe writer pole 120 allows for temperature sensing at the close pointdefined between the writer 110 and the magnetic recording medium 101(i.e., the writer close point). Temperature sensing at the writer closepoint also provides for sensing of changes in head-media spacing andcontact events at the writer region of the transducer 100.

In accordance with some embodiments, such as that illustrated in FIG. 8and discussed in detail hereinbelow, a thermal sensor may be positionedproximate the reader 140. Positioning a thermal sensor near the reader140 allows for temperature sensing at a close point defined between thereader 140 and the magnetic recording medium 101. Temperature sensing atthe reader close point provides for sensing of changes in head-mediumspacing and contact events at the reader region of the transducer 100.It is understood that some embodiments of the transducer 100 incorporatethermal sensing only at the writer, while other embodiments incorporatethermal sensing at the writer and other locations of the transducer,such as the reader 140 and/or a location away from the ABS 105 (e.g., areference thermal sensor).

According to various embodiments, the thermal sensor 116 is configuredto sense changes in heat flow for detecting head-media spacing changesand contact and, in some embodiments, asperities of the medium 101. Forexample, bias power can be applied to the thermal sensor 116 to raisethe surface temperature of the sensor and an adjacent portion of thetransducer 100 to be substantially higher than the temperature of themagnetic recording medium 101. An air gap is defined between the hottransducer surface and the relatively cool magnetic recording medium101. The transducer 100, air gap, and magnetic recording medium 101define one level of heat transfer rate. When the transducer 100 is incontact with the recording medium 101, such as after activation of oneor both of the thermal heaters 112, 142, the direct contact between thehigh thermal conductivity materials of the transducer 100 and therecording medium 101 significantly increases the heat transfer rate. Assuch, the thermal sensor 116 senses a drop of temperature or anexcursion of temperature trajectory, allowing for detection ofhead-media contact.

According to a representative example, the temperature profile of thetransducer 100 can be represented as a steady state DC signal generatedby the thermal sensor 116. In some embodiments, the temperature profileof the transducer 100 can be represented as an AC signal generated bythe thermal sensor 116, such as in response to modulation of head-mediaspacing for example. When the transducer 100 is actuated by one or bothof thermal actuators 112 and 142, the transducer surface temperaturewill increase with the actuation due to the generated heat. Thetransducer temperature will be higher than the temperature of therecording medium 101. As such, the recording medium 101 acts as a heatsink in this scenario. When the transducer 100 contacts the recordingmedium 101, the transducer surface temperature will drop due to a changein heat transfer rate resulting from the contact. The transducer surfacetemperature will continue to increase due to thermal actuator heatingand frictional heating. The change in temperature or excursion intemperature trajectory can be used to declare head-media contact.

According to various embodiments, the thermal sensor 116 of the writer110 is configured as a resistance thermal sensor. A resistance thermalsensor is essentially a thermal sensitive resistor on a pole tip. Aresistance thermal sensor measures the temperature change induced by allthermal condition changes from air pressure, clearance, and contact,among other changes. For the air bearing 105 of transducer 100 shown inFIG. 1, for example, transducer cooling efficiency improves with reducedclearance to the medium 101 due to an increase in thermal transportefficiency. Transducer cooling efficiency reaches a maximum when thetransducer 100 contacts the medium 101 because the medium 101 providesan efficient thermal sink to the transducer 100.

Although the thermal sensor 116 can be implemented using differenttechnologies, the thermal sensor 116 is described herein as a resistancethermal sensors composed of materials having a temperature coefficientof resistance (TCR) according to various embodiments. Other types ofthermal sensors can be employed, such as a varistor or a thermocouple,for example. One example of a TCR sensor is a dual-ended temperaturecoefficient of resistance sensor (DETCR), in which each end is coupledto a bias source (e.g., bond pad of the transducer). Another example ofa TCR sensor is a ground-split (GS) temperature coefficient ofresistance sensor, in which one end of the GSTCR is coupled to groundand the other is coupled to a bias source. A TCR sensor measurestemperature change by measuring the change in resistance, or rate ofchange in resistance, across the sensor. The thermal sensor 116 situatednear or at the ABS 105 are configured to measure the temperature changeat ABS 105 induced by all thermal condition changes from air pressure,clearance, head operation, and contact, among other changes.

According to various embodiments, and with reference to FIG. 2, methodsof the disclosure involve provision of a temperature sensor at or near ashield of a writer. Some embodiments involve providing a temperaturesensor at or near a return shield of a return pole of the writer. Otherembodiments involve providing a temperature sensor within a section of awriter core of the writer which includes a write gap. The methodaccording to FIG. 2 further involves sensing 204 temperature at or nearthe shield using the temperature sensor. The method also involvesmeasuring 206 a change in the sensed temperature. The measuredtemperature change 206 may be used to perform a variety of functions orpredetermined actions 208.

FIG. 3 is a flow chart showing various processes involving detection ofcontact between a transducer and a magnetic recording medium inaccordance with various embodiments. The method shown in FIG. 3 involvessensing 302 temperature at or near a return shield of a writer using atemperature sensor. The method also involves measuring 304 a change inthe sensed temperature, and detecting 306 spacing changes and/or contactbetween the transducer and the magnetic recording medium in response tothe measured temperature change.

In accordance with other embodiments, and with reference to FIG. 4,methods of the disclosure involve providing 402 a thermal sensor at ornear a return shield of a writer return pole of a transducer. Variousoperations can be performed depending on whether or not data needs to bewritten to a magnetic recording medium proximate the transducer. Duringa time in which data needs to be written 404 to the magnetic recordingmedium, the thermal sensor is used to enhance the data writing process.According to some embodiments, after energizing 410 the coils of thewriter, writing data to the magnetic recording medium involvessynchronizing 412 the magnetic response of the writer pole and thereturn shield(s) when writing data to the magnetic recording medium. Forexample, a control circuit (see FIG. 8, for example) can be configuredto actively synchronize magnetic response of the writer pole and thereturn shield(s) during write operations, so as to enhance or optimizethe magnetic write field gradient and mitigate side track erasure.Synchronizing the writer pole in this manner and establishing a fluxcircuit with the shield(s) closing the flux circuit enhances writeaccuracy, ensuring that a supplied magnetic write field will achieve afast and sharp transition between two bits. It is noted that using thethermal sensor to facilitate synchronizing of the magnetic response ofthe write pole and the return shield(s) during write operations involvespassing a relatively large current through the thermal sensor (e.g.,about 20 mA to about 100 mA, DC or AC).

During a period of time in which data does not have to be written 404 tothe magnetic recording medium, the thermal sensor can be used for avariety of functions, such as sensing head-medium separation andhead-medium contact, determining fly height and adjusting same, anddetecting asperities, avoids, and other topological features of themagnetic recording medium. Other functions that can be performed usingthe thermal sensor include sensing a change in modulation of the flyingtransducer or slider and measuring a change in thermal conductivities.According to the representative embodiment shown in FIG. 4, operationsperformed during a period in which data writing is not needed involvessensing 420 temperature at or near a return shield using the temperaturesensor, measuring 422 a change in the sensed temperature, and detecting424 spacing changes and/or contact between the transducer and themagnetic recording medium. It is noted that using the thermal sensor tofacilitate various sensing and measuring operations during periods notinvolving data write operations involves passing a relatively smallcurrent through the thermal sensor as compared to current suppliedduring write operations (e.g., about 0.1 mA to about 25 mA).

FIG. 5A is a sectional view of a writer core 500 which incorporates athermal sensor in accordance with various embodiments. According to theembodiment shown in FIG. 5A, the writer core 500 is a component of atransducer configured to interact with a magnetic recording medium. Thewriter core 500 includes an upper core portion 510 comprising coils 512and a lower core portion 530 comprising coils 532. The upper core 510includes a writer return pole 513, and the lower core 530 includes awriter return pole 531. The writer return pole 513 includes an upperreturn shield 514, and the writer return pole 531 includes a lowerreturn shield 534. In some embodiments, the upper core 510 is situatedcloser to the trailing edge of the transducer than the lower core 530.

A writer pole 520 is shown situated between the upper and lower cores510 and 530. For purposes of explanation, a dotted line (extendinghorizontally across FIG. 5A) is shown passing through an axis of thewriter pole 520, which demarcates the upper core 510 from the lower core530. A vertically oriented dotted line in FIG. 5A indicates the locationof the air bearing surface 505 of the transducer on which the writercore 500 resides.

The upper core 510 includes a writer gap 519 defined between a distalend of the return shield 514 and the writer pole 520. In the embodimentshown in FIG. 5A, a thermal sensor 516 is situated within the upper core510 of the writer core 500. As shown in FIGS. 5A and 5B, the thermalsensor 516 is situated adjacent the return shield 514 near the writerpole 520. Although spaced apart from the return shield 514 in thisembodiment, the thermal sensor 516 is sufficiently close to the returnshield 514 such that the temperature and changes in temperatureexperienced by the thermal sensor 516 are the same or substantially thesame (e.g., to within about 0.1° C. to about 10° C.) as that experiencedby the return shield 514. In particular, in the embodiment shown in FIG.5B, the thermal sensor 516 is situated adjacent a distal end of thereturn shield 514 proximate the gap 519. Because the return shield 514is situated at or near the ABS 505 and at or near the writer closepoint, the temperature and temperature changes of the thermal sensor 516are the same or substantially the same as that experienced by the returnshield 514 and the writer close point.

According to various embodiments, the thermal sensor 516 is situatedwithin the upper core 510 of the writer core 500 and spaced apart fromthe writer pole 520 by less than about 500 nm (e.g., about 1 nm to about500 nm). In various other embodiments, the thermal sensor 516 issituated within the upper core 510 of the writer core 500 and spacedapart from the writer pole 520 by less than about 400 nm, 300 nm, 200nm, 100 nm, and 50 nm, respectively. For example, and according tovarious embodiments, the thermal sensor 516 is situated within the uppercore 510 of the writer core 500 and spaced apart from the writer pole520 by between about 20 and 500 nm. In some embodiments, for example,the thermal sensor 516 is situated about 200 to 300 nm from the writerpole 520. In other embodiments, the thermal sensor 516 is situated about100 to 200 nm from the writer pole 520. In further embodiments, thethermal sensor 516 is situated about 50 to 100 nm from the writer pole520. In yet other embodiments, the thermal sensor 516 is situated about20 to 50 nm from the writer pole 520.

In accordance with various embodiments, the thermal sensor 516 is spacedapart from the return shield 514 by at least about one nanometer. Forexample, and as best seen in FIG. 5B, the thermal sensor 516 may bespaced away from the return shield 514 by about 1 to 20 nm, such asbetween about 2 and 10 nm. The thermal sensor 516, as discussedpreviously, may be configured from materials having a temperaturecoefficient of resistance, such as Pt, Ru, Ni, and NiFe, for example.

FIG. 6 illustrates a thermal sensor 616 of the type described previouslyin FIGS. 1 through 5. According to various embodiments, the thermalsensor 616 can be fabricated as a wire formed of one or more materialshaving a relatively high TCR. As generally shown in the figures, thethermal sensor 616 can have a square or rectangular cross-sectionalshape, although other cross-sectional shapes are contemplated includingother polygonal and curved shapes. In FIG. 6, the thermal sensor 616 hasa thickness, z, a depth, y, and a width, x. According to someembodiments, the thermal sensor 616 can have a thickness of about 35 nm,a depth of about 200 to 400 nm, and a width of about 1.5 to 3 μm. Itwill be appreciated that the thickness, depth, and width (or otherdimensions) of the thermal sensor 616 will vary depending on theparticulars of the writer core design.

In accordance with various embodiments, and with reference to FIG. 7, athermal sensor 716 may be incorporated within the upper core 710 of awriter core 700 and operate as a multiple-purpose component of thetransducer. FIG. 7 is a sectional view of a writer core 700 of atransducer that incorporates a thermal sensor 716 and circuitry745/750/755 that controllably powers the writer core 700 and thermalsensor 716 in accordance with various embodiments. In one mode ofoperation, the thermal sensor 716 serves as a temperature sensor similarto those described previously with regard to FIGS. 5 and 6. In anothermode of operation, the thermal sensor 716 operates cooperatively withthe writer pole 720 to amplify and contain a magnetic field during writeoperations to enhance transition sharpness. During write operations, themagnetic response of the writer pole 720 and the return shield 714 (andoptionally the return shield 734) is actively synchronized using thermalsensor 716. When operating as a thermal sensor, the thermal sensor 716is supplied a relatively low current, such as that identifiedhereinabove. When used during write operations, the thermal sensor 716is supplied a relatively high current, such as that identifiedhereinabove.

FIG. 7 is a sectional view of a writer core 700 which incorporates athermal sensor within or inside a shield of the writer core 700 inaccordance with various embodiments. It is understood that embodimentsincorporating a multi-purpose thermal sensor 716 can locate the thermalsensor 716 in a spaced-apart relationship with respect to the returnshield 714, such as is shown and described with regard to the embodimentshown in FIGS. 5-6. According to the embodiment shown in FIG. 7, thewriter core 700 is a component of a transducer configured to interactwith a magnetic recording medium, and includes an upper core portion 710and a lower core portion 730. The upper core 710 includes coils 712 anda upper return shield 714, and the lower core 730 includes coils 732 anda lower return shield 734. The upper core 710 is situated closer thanthe lower core 730 to the trailing edge of the transducer according tosome embodiments. A writer pole 720 is situated between the upper andlower cores 710 and 730.

In the embodiment shown in FIG. 7, the thermal sensor 716 is situatedwithin or inside the return shield 714 of the upper core 710 of thewriter core 700. More particularly, the thermal sensor 716 is situatedwithin or inside a distal end of the return shield 714 proximate the gap719. Because the return shield 714 is situated at or near the ABS 705and near the writer close point, the temperature and temperature changesof the thermal sensor 716 are the same or about the same as thatexperienced by the return shield 714 and the writer close point.

According to some embodiments, the writer core 700 is implemented as acompact core. Compact cores demonstrate performance benefits in responseto a reduced write field rise time (that is, how fast the writer poleresponds to a change in direction of the coil field). Writer coils 712and 732, for example, may be implemented close to the ABS 705 forpurposes of reducing write field rise time. However, changing writefield rise time does not necessarily affect gradient rise time (that is,how quickly the writer structure can achieve an ideal gradient). Thewrite field is determined mostly by a writer pole 720, but the gradientdepends on the response of the writer structure. The gradient rise timeis typically much slower than the write field rise time, and depends notonly on the writer pole speed, but also on how fast the return shield(s)can close the flux circuit to establish the write field gradient.Compact core designs, however, demonstrate substantial risk of sidetrack erasure (that is, writing to adjacent tracks).

In accordance with the writer core embodiment illustrated in FIG. 7, thecoil arrangement 712, 732 generates a magnetic field that is energizedand field amplified by a thermal sensor 716 positioned in the vicinityof the writer pole 720. The thermal sensor 716, which may be implementedas a wire formed of a material having a thermal coefficient ofresistance, can generate large local magnetic fields by way ofrelatively large current densities in the wire. The field profile fromthe thermal sensor wire 716 maps onto that of the writer pole 720 toyield enhanced field gradients. The thermal sensor 716 is energizedusing a current flowing in the direction opposite to current flowing inthe writer core coils 712 and 732. This current generates a magneticfield to actively synchronize the magnetic response of the writer pole720 with the return shield 714 and/or other shield(s) (e.g., returnshield 734 during write operations.

The magnetic field can be confined in the cross-track direction usingthe magnetic shields of the writer core 700 and/or field cancellationusing other magnetic fields generated at the writer core 700. Inaddition, a higher current density in the thermal sensor wire 716 may beused to produce a strong side field with polarity opposite that of thewriter pole 720. This effect, in combination with the soft magneticmaterial of the shields, results in reduced side effects, goodcross-track field confinement, and shielding adjacent tracks. Becausethe shields can also act as heat sinks for the thermal sensor wire 716,the magnetic material of the shield should have good thermal properties.

The materials used to manufacture the thermal sensor wire 716 mayinclude any of a wide variety of conventional electrical conductors thathave a TCR. In general, materials having a relatively high TCR providefor enhanced temperature and temperature change sensing by the thermalsensor wire 716. However, materials having a relatively low TCR canprovide sufficient temperature sensing resolution in embodiments of amulti-purpose temperature sensor 716. Suitable materials for fabricatingthe thermal sensor wire 716 include, but are not limited, metals such asPt, Ru, Cu, Au, Al, W, Ni, NiFe, and Mo. Other non-metal materials mayalso be used, such as carbon nanotubes, indium tin oxide (ITO),Poly(3,4-ethylenedioxythiophene) (PEDOT), poly(styrene sulfonate) PSS,and graphene. In some embodiments, the material may be selected to havea small coefficient of thermal expansion so that the size can becontained even when heat is generated by the current flowing through thethermal sensor 716.

The current supplied to the thermal sensor 716 can be similar to thatprovided to the writer core coils 712 and 732, or may be different(e.g., different waveform and/or different magnitude). Heat generated athigh-current densities can be dissipated through the cooling poweravailable at the ABS 705 for a transducer in flight. This cooling poweris already coupled with the transducer head due to the large surfacearea of the recording media relative to the transducer. The thermalsensor 716 can be energized using any suitable source, including but notlimited to a current source 750. In one illustrative example, thethermal sensor 716 is energized by the same current source 750 used toenergize the writer core coils 712 and 732. In another illustrativeexample, current in the thermal sensor 716 can be driven independentlyof the writer core coils 712 and 732, such as by a second current source755. In such an implementation, the current source 755 is used toestablish a current in the thermal sensor 716 independent of the currentbeing provided to the writer core coils 712 and 732 by current source750. Using an independent current source 755 enables properties of thecurrent (e.g., waveform, amplitude, and phase) to be “fine-tuned” forthe thermal sensor 716, for example, based on operating conditions and afeedback loop.

FIG. 7 further shows a control circuit 740 configured to activelysynchronize a magnetic response of the writer pole 720 and the shield(s)714/732 in accordance with various embodiments. In one illustrativeimplementation, actively synchronizing a magnetic response of a writerpole 720 and shield 714 is performed by control circuit 740 located offof the transducer to energize one or more writer coils 712/732. Inanother illustrative implementation, the control circuit 740 is locatedon or within the transducer. Combinations of off-transducer andon-transducer control circuitry may also be employed. The controlcircuit 740 includes or is coupled to an energizing source, which may bethe current source 750, current source 755 or other current source. Thecontrol circuit 740 may include a sensor module 745 configured toreceive input from the thermal sensor wire 716 and/or theelectromagnetic field being generated by the thermal sensor wire 716.The sensor module 745 of the control circuit 740 can also receive inputfrom other sources. Input received by the sensor module 745 is processedand used to make adjustments to the output of the current source(s)750/755. For example, the input at sensor module 745 may be used forphase adjustment, amplitude adjustment, and/or waveform adjustment ofthe current signal.

In accordance with various embodiments, and with reference to FIG. 8, arecording transducer 800 is shown to include a multiplicity of thermalsensors 816 and 880. The recording transducer 800 includes a number ofother components, including a writer 802 (which includes an upper writercore 810 and a lower writer core 830), a writer heater 840 thermallycoupled to the writer 802, a reader 850, and a reader heater 860thermally coupled to the reader 850. The writer 802 and reader 850 arepositioned at or near an ABS 805 of the transducer 800. Thermalactuation of the writer heater 840 causes thermal expansion of thewriter region of the transducer 800, resulting in reduced spacingbetween the writer 802 and an adjacent magnetic recording medium.Actuation of the reader heater 860 causes thermal expansion of thereader region of the transducer 800, resulting in reduced spacingbetween the reader 850 and the adjacent magnetic recording medium.Thermal actuation of the writer and reader regions of the transducer 800causes the writer and reader thermal sensors 816 and 880 to becomesituated at or extremely close to the writer and reader close points,respectively. The writer and reader heaters 840, 860 and the thermalsensors 816, 880 can be selectively activated to control head-mediaspacing in a data storage system.

According to the embodiment of FIG. 8, the transducer 800 incorporates athermal sensor 816 within a writer core 802, and a thermal sensor 880situated at or near the ABS 805 adjacent a reader 850 of the transducer800. The thermal sensor 880 adjacent the reader 850 is configured tosense for temperature and temperature changes at the reader region ofthe transducer 800. As discussed previously, the thermal sensor 816 isconfigured to sense for temperature and temperature changes at thewriter region of the transducer 800. The thermal sensors 880 and 816 canbe of the same or different technology. For example, each of the thermalsensor 880 and 816 can be fabricated with material having a TCR.

In some embodiments, the thermal sensor 816 is situated within an uppercore 810 of the writer core 802 at a location spaced apart from a returnshield 814 of the writer core 802. In other embodiments, the thermalsensor 816 is situated within or inside the return shield 814 of theupper writer core 810. In such embodiments, the thermal sensor 816 canbe configured to operate in multiple modes, including a temperaturesensing mode (e.g., for spacing change and contact detection) and a modefor enhancing or optimizing the magnetic field gradient when writingdata to a magnetic recording medium. Bias power can be supplied to thethermal sensor 880 adjacent the reader 850 by the same or a differentsource that supplies bias power to the thermal sensor 816 within thewriter 802. In accordance with embodiments in which the thermal sensor816 is a multiple-purpose component, the thermal sensor 816 is suppliedbias power from a source capable of supplying relatively high currentneeded for enhancing or optimizing the magnetic field gradient duringdata writing operations.

The thermal sensors 816 and 880 can be connected to separate powersources or the same power source. In some embodiments, the thermalsensors 816 and 880 can be connected in series. In other embodiments,thermal sensors 816 and 880 can be connected in parallel, such as via aground-split connection approach as previously described. Although thethermal sensors 816 and 880 can be connected to separate power sources,connecting the thermal sensors 816 and 880 in series or parallelprovides for a reduction in the number of transducer bond pads neededfor these components. It is understood in the art that adding bond pads(e.g., a current source contact, a voltage source contact, groundcontact) to a transducer can require an extensive and expensivere-design of the transducer, adding cost and fabrication complexity.

According to some embodiments, the temperature profile of the transducer800 can be represented as a steady state DC signal generated by thethermal sensors 816 and 880. In other embodiments, the temperatureprofile of the transducer 800 can be represented as an AC signalgenerated by the thermal sensor 816, such as in response to modulationof the heater power for example. When the transducer 800 is actuated byone or both of thermal actuators 840 and 860, the transducer surfacetemperature will increase with the actuation due to the generated heat.The transducer temperature will be higher than the temperature of theadjacent recording medium, causing the recording medium to act as a heatsink. When the transducer 800 contacts the recording medium, thetransducer surface temperature will drop due to a change in heattransfer rate resulting from the contact. The transducer surfacetemperature will continue to increase due to thermal actuator heatingand frictional heating. The change in temperature or excursion intemperature trajectory sensed by the thermal sensors 816 and 880 can beused to declare a head-media contact event at one or both of the writerand reader regions of the transducer 800.

It is to be understood that even though numerous characteristics ofvarious embodiments have been set forth in the foregoing description,together with details of the structure and function of variousembodiments, this detailed description is illustrative only, and changesmay be made in detail, especially in matters of structure andarrangements of parts illustrated by the various embodiments to the fullextent indicated by the broad general meaning of the terms in which theappended claims are expressed.

1. An apparatus, comprising: a writer core of a transducer, the writercore configured to interact with a magnetic recording medium andcomprising an upper core and a lower core; at least one of the upper andlower cores comprising a return pole having a return shield; a writerpole between the upper and lower cores; a writer gap defined between thewriter pole and the return shield; and a sensor element within one ofthe upper and lower cores that includes the writer gap, the sensorelement having a temperature coefficient of resistance and configured tosense for a change in temperature indicative of one or both of a changein spacing and contact between the transducer and the magnetic recordingmedium.
 2. The apparatus of claim 1, wherein the sensor element isspaced apart from the return shield.
 3. The apparatus of claim 1,wherein the sensor element is integral to the return shield.
 4. Theapparatus of claim 1, wherein the sensor element is at or near a distalend of the return shield proximate the writer gap.
 5. The apparatus ofclaim 1, wherein: a portion of the return shield is at or near anairbearing surface of the transducer; and the sensor element is spacedapart from the return shield portion and away from the airbearingsurface.
 6. The apparatus of claim 1, wherein: the apparatus comprises aleading edge and a trailing edge; and the upper core is situated moreclosely to the trailing edge than the lower core.
 7. The apparatus ofclaim 1, further comprising a reader of the transducer, wherein: thereader is situated more closely to the lower core than the upper core;and the upper core comprises the return shield.
 8. The apparatus ofclaim 1, wherein: the sensor element is spaced apart from the returnshield; and the spacing between the sensor element and the return shieldallows for a change in temperature at the return shield resulting fromone or both of the spacing change and contact to be sensed by the sensorelement.
 9. The apparatus of claim 1, wherein: the sensor element isspaced apart from the return shield; and the spacing between the sensorelement and the return shield is such that a change in temperatureexperienced by the thermal sensor is the same or substantially the sameas that experienced by the return shield.
 10. The apparatus of claim 1,wherein the apparatus comprises a writer heater proximate the writercore and configured to thermally activate at least the writer pole, thereturn shield, and the sensor element.
 11. The apparatus of claim 1,wherein the writer core further comprises a spacer between the thermalsensor and the return shield, the spacer comprising a material having atemperature coefficient of resistance.
 12. The apparatus of claim 1,wherein the sensor element is separated from the writer pole by lessthan about 300 nm.
 13. The apparatus of claim 1, wherein the sensorelement is configured to sense one or both of a change in modulation ofthe transducer during flight and a change in thermal conductivities. 14.An apparatus, comprising: a writer core of a transducer, the writer coreconfigured to interact with a magnetic recording medium and comprisingan upper core and a lower core; at least one of the upper and lowercores comprising a return pole having a return shield; a writer polebetween the upper and lower cores; a writer gap defined between thewriter pole and the return shield; and a sensor element within one ofthe upper and lower cores that includes the writer gap, the sensorelement having a temperature coefficient of resistance and configuredto: sense for a change in temperature indicative of one or both of achange in spacing and contact between the transducer and the magneticrecording medium; and enhance a gradient of a magnetic field generatedby the write core.
 15. The apparatus of claim 14, wherein thetemperature sensor is integral to the return shield.
 16. The apparatusof claim 14, wherein the sensor element is configured to: sense, in afirst mode, for the change in temperature indicative of one or both ofthe change in spacing and contact between the transducer and themagnetic recording medium; enhance, in a second mode, the magnetic fieldgenerated by the write core; and the first and second modes areseparated in time.
 17. The apparatus of claim 14, comprising circuitrycoupled to the writer core and configured to actively synchronizemagnetic responses of the write pole and the return shield during writeoperations.
 18. A method, comprising: sensing a temperature at or near areturn shield of a writer core of a transducer; measuring a change inthe sensed temperature indicative of a change in spacing or contactbetween the transducer and an magnetic recording medium; and performinga predetermined action in response to the measured temperature change.19. The method of claim 18, wherein the predetermined action comprisesdeclaring a contact event between the transducer and the medium.
 20. Themethod of claim 18, further comprising: sensing the temperature at ornear the return shield using a thermal sensor; and enhancing a gradientof a magnetic field produced by the writer core using a magnetic fieldproduced by the thermal sensor.